Electric contact converter



1954 A. SCHMIDT, JR. ETAL ELECTRIC CONTACT CONVERTER Filed July 5. 19502 Shee ts-Sheet l Inventors:

S m s e E m W o m t c HH t S as A tmw r m 8 Q h C T A 9 b Dec. 14, 1954A. SCHMIDT, JR. ETAL 2,697,198

ELECTRIC CONTACT CONVERTER Filed July 5, 1950 2 Sheets-Sheet 2 I I I 3 lt f I d L IT I I I [I r ,5 :9 t k II I H *1' t 1 4 I I I I I f 1 f t ICAPACITOR HAQMON\C VOLTAGE PHASE CURRENTS TS PHASE VOLTAGE-5PRE5AT'URAT!NG 5 AMPERE. TURNS T1 L Inventors: August: SchmidtgJr;Charles H. Titus, Clicdius H. vviHis y Them Attorneg.

United States Patent cc 2,697,198

Patented Dec. 14, 1954 1 2 mutating reactors .to .be used to supplyrapidly changing loads. 2969x198 Still another object of the presentinvention is to pro- ELE CONTAQT CONVERTER vide precharged capacitancemeans for adding an ad- August Schmidt, 51:, Schenectady, N. Y.,(Zhanles H. Titus, of a contact ,type converter the; advancement ofwhich Philadelphia, Pa., and Clodius H. iWjllis, P i t varies inaccordance with variations in the load on the N. J., assignors to.General Electric Company, .a corpoconverter thereby o i provecommutation for r pi ly ration of New York changing load conditions.

" I In accordance with the invention, energy storage means A icat on-E y5, HSQSE QI-N 172,134 such as a capacitor ischarged at a predeterminedpolarity during each contact conducting period and such energy 9 C im(Cl- 32174.8

This invention relates to .electric contact converters e e Storage meansis arranged to he charged P pe an more a ti ul l t an 1m raved Commutatmreactionately to the load current and is so connected as to intor andlaid re i commuliatmg capacltor cofinbinacrease the instantaneous valuesof alternating voltage of tron for improving the commutatmg action ofsuch conthe 1I1e0m1hg Phase duflhg the Sueeeedlhg Contact Overlap veters under v bl l d mm period and to decrease the instantaneous valuesof such 11 mechanical rectifiers having cyclic overlappingcom- 2OVQltage of the Outgolhg P s dur g the Succeeding e011- mutatingcontacts, a short circuit in effect is established e Q l P h each Phaseof the altelhatlhg ellrlent during the time of contact overlap in orderto efiectitranstlh t ma the ate of transfer of current er 0f Curr ntfrom the outgoing phase to the incoming from the rectified contact foreach phase of the alternating P as Whi h tends to allow very large shortcircuit curcurrent circuit to the rectifier contact for the nextsucceedrents to circulate between the two phases during the com- 1% P356 8 made d pendent upon the magn tude f h mutating or contact overlapperiod Zln electronic conload h Slhee the maghhude of the chargeSupplied verteis this short circuit current is prevented from betheenergy Storage means 15 dependent upon the QOIIllIlg excessive due tothe inherent valve action of th hlthde Of the l d Current prior to thesucceeding overlap I v n I therefore necessary that somemeans beemployed where- Cehhhutahoh when rapid and suhstahhal load changes y thecurrent in the outgoing phase is limited in mage nitude when theoutgoing phase contact opens at the end h accordance with the presentinvention means 0 t e Commutatmg or Contact ovfirlap period oneincluding control windings are provided for co-operating iangement foraccomplishing this purpose employs satur- W the load current respohslvecapacitance means In a 16 reactors arranged to be unsaturated near theend of controlling the unsaturation of the load current saturablc 1ecommutatmg or Contact overlap penod when such reactors so as to maintainthe current in each phase Windlcactols are unsaturated the Impedance 18greater than ing circuit at small instantaneous values for a sufiicientwhen saturated so that by such means the decaying current hme Intervalafter the energy stonhg capacitance means m the outgomg phase 18mamtamed at or near Its Zero 5 effects the transfer of the load currenttherefrom to the value or an appreciable time that is dependent upontheehche-cchhg Phase Wlhdlhg c1rcu1t to hchlde the end of the voltsecondcapacity of the reactors thereby facilitatinr hredetenhmed ClosureOverlap of the Correspohdmg the interruption of current upon the openingof the con tact? As a result of thls cooperahhg relahohshlp the tact ineachoutgoing phase to end 1 e contact voverla rechher cohtaits 9 Qphh toe predeiermhed clhsure period after. current is built upinthenextiincom'ing phase Overlap penods ih deletenous eparkmg underWidely to e rendered conductive. Whenever the load on a con- Yht g e hgf h f verter with constant contact overlap periods changesand g S ge-rstah h1g0 g e lhvehhohil 2 5? particularly when the loadchangesrapidly commutation m I a 9 he accomphhymg rawlhgs In W 1C1 i icuities are aggravated unless relatively large.volt -sec- SC emeticrepresentation 0 a Contact converter 0nd capacity Commutatmg reactorsare employed 3) bodying the invention Fig 1a is a schematic representanoob ect of this invention is to provide an improved hon of a pomoh of F 1and a modlhcahoh thereto; load responsive commutating system forreducing the duty h 1h Whlch F 1g 2 1s a group of curves d1 awn to thesame Imposed upon the commutatmg reactors of mechanic-a1 time scale foraiding in understanding the arrangement contact converters under varyingload conditions 5 f i 1h 1 f b t th M t Another obJect of the Presentinvention is to facilitate 3 h 1g t e h g er 0 g e 3 E i commutation Ina mechanical contact type converter by lhgicurreht Chem eslghate as 2 an3 an t e supenmposmg a prechanged capacltor Voltage that direct currentc1rcu1t DC1 and DC-2 is effected through cieases with the load upon thevoltage of the alternating the'swltch the transformer havlhg a prhharyWlhchhg current circuits of the converter so as to effectively ad- Th asccohhar-y wl-hdlhg the Contact mechahlsm C vance the productionof .acommutating diflerential in (X0 g suecesslve .Cohtact overlap periods 9constant voltage between the contacts undergoing commutation and duhahohas degtcrhhhedtby the shape of the used porhoh thereby acceleratethetransfer of theloadcurrent from h l h t e t reactors R1 and R2, andthe each contact to the next succeeding contact to be rendered f h r-ahsTP h b 0 conductive proportionately to the-increase of the load ihpr-hhary Tans Onher Wm mg Own elhe Current. delta-connected and thesecondary Winding TS is ar- A further object of this :invention is toprovide load hahghd as a slvx'phase star connected h Connectedresponsive prechargedcapacitance means for producing $0. hatt f eg g ofWmdmg 1g h advancement of the commutating voltage for facilitating z 2erre y trans ormeh ti to t 6 g commutation III a polyphase overlappingcontact converter 1 en t g a f f t a Tech er an employing load currentsaturablereactors to insure that ig g i t fg gg gg g g a g g g i gii i eective.unsaturation -of the'load current saturable ree 0 I the contacts-16 of device C as indicated. actors Occur h eohtiacts open en P ed Forthe: purpose of operating the contacts 1-6 in overhhhed overlap 'P uhder-e vet tt e ea hd lapping succession or sequence, a cam member 7 havinga Q raised portion 8 is mounted on the shaft 9 which in turn. is A h h hhl Q th1 l Ye t eh thep cvls b driven by the motor M. Motor-M isenergized from the of an mprov ed load responsiveconimptatiop capacitoalternating current circuit and is of the synchronous tyne. prechargingarrangement for ,contact type v converters Each of thecontacts 1-6 isprovided with a biasing spring which is particularly adapted forenabling mechanical .conwhich biases the contact toward the openposition. When V v V v v A the raised portion'fi of cam 7 sequentiallyengages the periods and relatively sm all volt-second capa cit-yconicontacts 1-6, a circuit is alternately completed from one I resentedin Fig. 2 by of one of the reactors R1 or by so that build-up of currentthrough contacts 1 of the six-phase windings of the secondary winding TSto the conductor 10 and to the conductor 11. it will be observed thatwith the parts in the position shown, a circuit is completed from theterminal in of the winding TS through contacts 1 to conductor 10.Rotation of cam 7 in the counterclockwise direction will subsequentlybring raised portion 8 of cam 7 into engagement with contact 2 and hencewill close that contact before contact 1 is opened thereby completing acircuit between terminal 2a of winding TS through contacts 2 toconductor 11. Thus, it will be seen that current is drawn from windingTS by sequentially completing a circuit through the appropriate one ofthe contacts 1-6 so that successive phases 1a, 2a, 3a, 4a, 5a, and 6a ofwinding TS will supply current through the corresponding successivelyclosed overlapping contacts of device C when the converter is operatedas a rectifier. The polyphase windings 7a, 2a, 3a, 4a, 5a, and 6a of thetransformer secondary TS have successive phase voltage induced thereinand thus will successively supply rectified load current to the directcurrent circuit DC-1 and 2 as each of the series of contacts 16 hascircuit connections efiective upon the closure of the contact forinterconnecting a corresponding phase Winding with the load circuit tosupply load current thereto during the closure of the contact. Since thecontacts 1-6 are sequentially closed and opened by the synchronizing cam8 in a predetermined overlapping succession or sequence to provide apredetermined closure overlap of the successive contacts, theinterconnection of the corresponding successive phase windings with theload circuit will overlap so that each phase winding will beinterconnected in shunt or parallel with the succeeding phase windingfor transfer of the load current therebetween during the predeterminedclosure overlap of the corresponding contacts. It will also be observedthat conductors 10 and 11 as well as the commutating reactors R1 and R2are alternately energized, for example, conductor ill and reactor R1 areenergized upon closing of contacts 1, 3 and S and conductorll andreactor R2 are energized upon closing of contacts 2, 4 and 6. Currentsupplied to conductor 10 is fed through the saturable reactor R1 andthrough the left-hand portion of the harmonic auto-transformer HT to thedirect current line DCl when the device is being operated as a rectifierand in the reverse direction when the device is operated as an inverter.It will also be observed that current is allowed to flow betweenconductor 11 and the direct current conductor DC1, through the saturablereactor R2 and through the right-hand portion of the harmonicauto-transformer HT.

Saturable reactor R1 is for the purpose the outgoing phase current atsmall instantaneous values for an appreciable time during which time 3and 5 may be opened to end each corresponding contact overlap periodunder normal load conditions without difiiculty. Likewise, the reactorR2 is for the purpose of facilitating the interruption of current flowwhen contacts 2, 4 and 6 are opened to end each corresponding contactoverlap period under normal load conditions. These reactors may beprovided respectively with control windings 12 and 13 which areenergized from a source of alternating current potential such as thegenerator G driven by the motor M through shaft 9. Current fromgenerator G to windings 12 or 13 may be regulated by the adjustableimpedance 14. By suitable adjustment of the device 14, a degree ofpre-saturation of reactors R1 and R can be established so that thebuild-up of normal full load current through the main winding ofreactors R1 and R2 is facilitated due to the reduced impedance of thesecomponents caused by saturating current through windings 12 and 13. Whenthe current in these reactors R1 and R2 is reduced or caused to changepolarity near the end of the contact overlap period, the reactors becomeunsaturated and as a result their impedance will be increasedsubstantially. This increased impedance can be eifectively utilized tolimit the current flow in the outgoing phase through the associated oneof the contacts 1-6 to a low value when the contacts are opened to endthe corresponding contact overlap periods. The magnetizing ampere turnsdue to coils 12 and 13 are repthe curve in and the flux condition R2 isrepresented by the curve 1'.,}1Thus at time t1, the presaturating ampereturns are represented by the point P and the fiux 1 is represented thepoint Q. At point Q, reactor R1 is almost saturated is facilitated.

of maintaining Cir The horizontal lines g, a, b, c, d, f, and g, overlapin time to indicate the corresponding contact overlap periods duringwhich any two successively operated contacts are both closed. Forexample, the line designated as a represents the closed condition ofcontacts 1 and the line labeled b represents the closed condition ofcontacts 2. Thus, both contacts 1 and 2 are closed during the contactoverlap interval of time beginning at t2 and ending at T1 which time isthe commutating period during which the load current flow is decreasedin the outgoing phase and built up in the incoming phase. Such transferof the load current requires some little time due to the inductanceinherent in the phase circuits. During this period, the presaturatingampere turns ni have a negtive value and hence tend to unsaturate thereactor R1 when the current in phase 1 has decreased to such a valuethat the ampere turns in windings R1 and 12 are approximately equal.This eifect causes an increase in the impedance of reactor R and slowsthe decay of current ii. In the same manner, the flux condition ofreactor R2, is controlled by the magnetizing and demagnetizing effectsof coil 13. The instantaneous values of current between points M and Nof curve ii are low in magnitude relative to the maximum instantaneousvalues of the current curve i1 and hence interruption of current flowwhen contact 1 is opened at a time such as T1 is facilitated.

For the purpose of accelerating the transfer of current from one of thecontacts such as 1 to another of the contacts such as 2 against theinherent retarding action of the phase circuit inductance during eachconstant contact overlap period, the energy storage device HC is used.To accomplish this purpose in accordance with the present invention, anenergy storing capacitance means is interconnected upon successiveclosure of contacts 16 in effective series or load current responsiverelation with the phase windings and the direct current circuit so as toaccumulate charges of opposite polarity proportional to the value of theload current flowing in the direct current circuit from successive phasewindings during the separate closure of the corresponding contacts andthereby produce voltages effective to transfer a corresponding value ofload current from each phase winding to the succeeding phase Windingupon parallel interconnection thereof during the predetermined closureoverlap of the corresponding contacts. As shown in Fig. l, the energystoring circuit means comprises a capacitor HC having an inductivedevice HT that is utilized for interconnecting the capacitor HC in loadcurrent responsive relation (i. e. effective series circuit relation)with the phase windings controlled by the contacts 16 so as toaccumulate the charges of opposite polarity proportional to the value ofload current flow from the successive phase windings. This harmoniccapacitor is interconnected between the conducting paths comprisingreactors R1 and R2 and hence accumulates a charge of one polarityproportional to the current flowing through reactor R1 and conductor 10prior to the succeeding contact overlap period and of opposite polarityproportional to the flow of current through reactor R2 and conductor 11prior to the next succeeding contact overlap period. This is due to thefact that when current flows from reactor R through the left-hand end ofthe winding of harmonic transformer HT to the line D01, the polarity ofthe capacitor changing current induced by this winding will be positiveon the left-hand terminal and negative on the right-hand terminal thuscausing the polarity of capacitor H0 at point A to be positive and atpoint B to be negative. The charge accumulated on the capacitor platesis represented by the curve 20 in Fig. 2 and is proportional to the loadcurrent. When contact 1 is closed, the driving voltage across winding e1of the secondary winding TS is represented by the curve er in Fig. 2. Ifthe voltage represented by the curve ec is added algebraically to thevoltage of curve 21, the resultant voltage may be represented as in Fig.2 by the dotted line curve 201. In Fig. 2, it will be observed that atthe time T current through contacts 1 is a maximum value and remain sountil time t2. During this period of maximum values for current ii, thevoltage ec is caused to change in polarity from a positive value throughzero to a negative value so that at time T the effective voltage cfcurve e1 is represented by the point X which point is less positive thanthe point X1 2 which would be representative of the voltage e1 at timeT1 if the voltage ec were not added. Thus, it will be seen that theeffective voltage tending to maintain current flow through contacts 1and associated components is reduced at time T1 when. contacts 1 aresize reactor and longer commutatingcontact overlap opened. S1nce themagnitude of the voltage ec. 1s 1n periods would be required. In likemanner transfer of capacitor I-IC is particularly eif ective andusefulduring spectively is facilitated. Since the frequency of the voltrapidly changing load conditions. In this way, the inter- 5 age ec isthree times the frequency of the voltages Cf1L6,

ruptlon of current flow through contacts 1 is facilitated. thecommutating voltage ec can be aptly termed a bar,- The point X is lesspositive than the point X1 2 due to monic commutating voltage. Thefrequency of the voltthe accumulation of a positive opposing charge atterage ec is determined ty the number of contacts and the minal A ofcapacitor HC. The negative charge of terharmonic voltage will changefrom one polarity to anminal B of capacitor HC in eifect increases thevalueof ther polarity between any two successive commutating voltage 2at time T1 so that the effective voltage causmg periods. When terminal Bof capacitor HC is positive bull -up of current is is represented by thepoint X and terminal A is negative transfer of current from conratherthan by point X1-2. The voltage which facilitates tacts 2, {Sand 6 tocontacts 3, 5 and 1 respectively is likethe build-up of current throughcontacts 2 and conductor wise facilitated.

1 is represented in Fig. 2 by the dotted line curve em. Instead of usingan auto-transformer such as HT of g 1 with the capacitor HC connectedacross the end terminal A of capacitor HC is represented by point Xwould be substituted for the portion of Fig l which is of Fig. 2 andthat the voltage of terminal B of capacitor enclosed by dotted lines. InFig. 1a a transformer HT-l HC is represented by the point of Fig. 2 attime T1. having a primary winding 15 and a secondary winding 16 It willfurther be understood that the potential of point is used. The capacitorHC may be connected across the A effectively diminishes the voltage ofcurve or during secondary winding 16 of transformer HT1 With the t ecommutatmg eriod between time 12 and time T1 and, rr ng m n f Fig 1 r hrr g m n f g 1 h that the potential of point B in efiect lncreases thepocapacltor HC is magnetically coupled with the portion tentlal of curvee2 during this same period so that curof the winding of transformer HTWl'llCll is conducting rent decay in reactor R1 is facilitated andcurrent build-up current at a particular instant. through reactor R2 isaided during the commutating period Since the magnitude of the instananeous va ues f the. represented by the ti e f f 1 th ti T voltage ec isa function of the magnitude of the currents Thus it will be understoodupon referring to Fig. 2 that it-is and of the time during which SuchCur s a at the beginning of the contact overlap time it the comlowed toflow, it will be understood that the invention is posite voltage e01resulting from the imposition of the Particularly applicable toCOW/filters Whose en C ncondenser voltage on the phase voltage e1 whenthe ditl'OHS y p y and Within Wide i scapacitor HC is charged by theload current of the par- While particular embodiments of the inventionhave ticular value indicated is exactly equal to the composite been s wa described, it l be vi us to those voltage 202 resulting from theimposition of the opposite Skilled in the art that various changes andmodifications condenser voltage upon the phase voltage e2. Thereaftermay be made without departing from the invention in its the compositevoltage ccl decreases while the composite r r aspects i therefore, innde in the ap voltage e02 increases. This produces an increasingdifpended claims to cover all such changes and modifications ferentialbetween the two composite voltages which is ef- 40 as fall within thetrue spirit and scope of the invention. fective to produce commutationof the load current from What we claim as new and desire to secure byLetters phase 1 to phase 2. In other words, this voltage difieren-Patent 0f he U ite Stat s is: tial produces the transfer of the loadcurrent i1 from L h combination. P l P l a ing Current supcontact a tocontact b which is closed in overlapping'rela p y Wrndrngs, a directcurrent circuit, means n l d g a tion with contact a from time :2 totime T1. As a result, plurality of contacts arranged to be closed in ppg as shown in Fig. 2 at time t2 the outgoing phase current Sequence forsynchronously connecting successive phase ii begin to de ea e and the inmin phase u ent 1 windings to supply current to the direct currentcircuit, egins to in r a S h ommut ti o t f of the first and secondconductors forming alternate conducting load current is producedentirely by the differential be- Paths for the HOW of Current fromSuccessive Phass Windtween the voltages ec and 602. Thu when the end oflugs to the direct current circuit, said conductors being th o t toverlap ti T1 i a hed at whi h t t connected to said contacts so as tobe alternately energized a is opened, all of the load current has beentransferred In response to the Sequential operation of Said contacts,from phase 1 to phase 2 due to the composite voltage an inductive deviceinterconnected between said conducdifferential and the saturable reactorR1 then becomes y and hill/111g a mld-connechon With e l ec Currentunsaturated and therefore effective at point In to main clrcult WhelBhYP 1011 of said deVlCfi 1S n gize tam the current 11 in the outgoingphase 1 near or at by the current in said first conductor and anotherportion the ero value unt l the onta t 1 is opened t 11111 T] of saiddevice is energized by the current in said second to end the t t overlape d Th even though a conductor, capacitance means interconnected betweensaid considerable voltage dliferential 18 produced between theConductors and Operative to accumulate a Charge of 0116 overlappingcontacts at the end of the contact overlap Polarity Proportional t0flurreht flowing lhrohgh Said first period as represented by thedifferent points X and X" Conductor and 0f pp P y pfopofhohal t0 suchvoltage is effective to overcome the circuit inductance feht flowing hFsaifi Second Conductor whereby the and decrease the flow of load currentin the outgoing Charged cohdlhoh 0f f Capacitance means Provides a phaseto substantially ero and build up th l d current voltage variablyefiectrve to transfer current from each m the incoming phase. As aresult only a relatively small Phase Winding t0 the succeidihg PhaseWinding in p volt-second capacity commutating reactor is required topornon to the load current, variable impedance m ns in maintain thecurrent in the outgoing phase at or near Eerie? With Q 0f 831dCOHdHCtOTS, and means r onlts zero value when the outgoing phase contactis opened tr011111" the Impedance of Said Varlahle lmpfidahlle means t0d h Contact Overlap peno so that the current through the associatedconductor is I casc th l d current h ld incl-ease i ll it) maintained atlow instantaneous values when the transfer then the charge accumulatedby the condenser HC will f current from h corrcspondlng phase Wrndrng tthe increase correspondingly and thereby produce a cone Succeedlhg p 'gWlhdl'hg Completedspondingly larger differential between the compositevolth Q 9m Polyphase alternating Current SH ages 1 d 2, Hence h di gl lply wmdmgs, a direct current circuit, switchin means voltagediflferential will be effective to complete the com including a P W ofContacts, 6HCh will! having t ti or t f of th increased l d current fcuit connections effective upon the closure thereof for phase 1 to phase2 during the same constant contact overl'htercohhecfihg Correspondinglihilsc Winding With the lap period. By thus super-imposing the loadresponsive direct current circuit to supply load current thereto,synccndcnser Voltage on th phase l a k d 1 chronous means for closingand opening the contacts in provement in commutation is obtained, sincethis enables a fiedetel'mihed Sequence tO pp y Current f a saturablereactor of a given capacity to successfully Cesslve P windings andProvide a predetermined maintain the outgoing phase current at or nearthe z o sure overlap of the corresponding contacts, first and secvaluefor the required time near the end of the contact 0nd conductorsinterconnected with the contacts to form overlap period irrespective ofvariations in the load curalternate conducting paths for the flow ofcurrent to the rent value. Otherwise, a larger volt-second capacity anddirect current circuit from the successive phase windings proportionalto current flowing through said first conductor and of opposite polarityproportional to current flowing through said second conductor wherebythe charged condition of said capacitance means provides a voltagevariably effective to transfer current from each phase winding to thesucceeding phase winding during of the corresponding contacts in protheclosure overlap portion to the load current, variable impedance means inseries with each of said conductors, and means for con-- trolling theimpedance of said variable impedance means so that the current throughthe associated conductor is maintained at low instantaneous values whenthe transfer of load current from each phase winding to the succeedingphase winding is completed during tne closure overlap of thecorresponding contacts.

3. In combination, polyphase alternating current sup- 1 ply windings, aincluding a plurality of contacts, cuit connections effective uponinterconnecting a corresponding phase direct current circuit, switchingmeans each contact having cirthe closure thereof for winding with thedirect current circuit to supply load current thereto, synchronous meansfor closing and opening said contacts in a predetermined overlappingsequence to supply current from successive phase windings, first andsecond conductors interconnected with said contacts conducting paths forthe flow of current to the load circuit from the successive phasewindings so as to be alternately energized in response to the sequentialclosure of said contacts, an inductive device interconnected betweensaid conductors and having a mid-connection with the load circuitwhereby one portion of said device is energized by the current in saidfirst conductor and another portion of said device is energized by thecurrent in said second conductor, and capacitance means inductivelycoupled with said device and operative to accumulate a charge of onepolarity proportional to current said first conductor and of oppositepolarity proportional to current flowing through said second conductorwhereby the charged condition of said capacitance means provides avoltage variably effective during from one to the other of saidconductors to oppose the flow of current in said one conductor and tofacilitate the flow of current in said other conductors in proportion tothe load current.

4. In combination, a polyphase alternating current rectifier having adirect current load circuit provided with 7 synchronous switching meansincluding a series of contacts opened and closed in a sequence toprovide a predetermined closure overlap of the successive contacts andpolyphase windings having successive phase voltages induced therein andinterconnected with the contacts to successively supply load-current tothe direct current circuit during the successive closures of thecorresponding contacts, saturable reactor means having connections withthe contacts for successive saturation by the load current supplied fromsuccessive phase rent circuit, energy storing capacitance means havingconnections controlled by the contacts for enabling the capacitancemeans during the separate closure of the successive contacts toaccumulate charges of opposite polarity proportional to the thecorresponding phase windings to the direct current circuit and forenabling the capacitance means to apply the voltages produced by saidcharges to transfer the flow of a corresponding value of load currentfrom each phase winding to the succeeding phase winding during thepredetermined closure overlap of the corresponding contacts, and meansincluding control windings for controlling the unsaturation of thesuccessively saturable reactor means to maintain the current in eachphase winding at small instantaneous values for a sufiicient timeinterval after the capacitance means effects the transfer of the loadcurrent therefrom to the succeeding phase winding to include the end ofthe predetermined closure overlap of the corresponding contacts.

5. A rectifier having in-combination,

to form alternate windings to the direct curvalue of the load currentflow from polyphase windthe transfer of current ings having successivephase voltages induced therein, a direct current load circuit, switchingmeans including a series of contacts, each contact having circuitconnections effective upon the closure thereof for interconnecting acorresponding phase winding with the load circuit to supply load currentthereto, synchronizing mechanism for periodically closing and openingthe contacts in a predetermined sequence to supply load currentfromsuccessive phase windings and provide a predetermined closureoverlap of the corresponding contacts, saturable reactor means havingconnections with the contacts for successive saturation by the loadcurrent supplied from the successive phase windings to the directcurrent circuit, capacitance means having connections controlled by thecontacts for enabling the capacitance means upon successive closure ofthe contacts to accumulate charges proportional to the value of the loadcurrent flow in the direct current circuit and for enabling thecapacitance means to apply the voltages produced by said charges totransfer a corresponding value of load current from each phase windingto the succeeding phase winding during the predetermined closure overlapof the corresponding contacts, and means including control windings forcontrolling the unsaturation of the successively saturable reactor meansto maintain the current in each phase winding at small instantaneousvalues for a sufficient time interval after the capacitance meanseffects the transfer of the load current therefrom to the succeedingphase winding to include the end of the predetermined closure overlap ofthe corresponding contacts.

6. An alternating current rectifier having in combination, polyphasewindings having successive phase voltages induced therein, a directcurrent load circuit, switching means including a series of contacts,each contact having connections effective upon the closure of thecontact for interconnecting a corresponding phase winding to supply loadcurrent through the contact to the direct current circuit, saturablereactor means having connections with the contacts for successivesaturation by the load current supplied from the successive phasewindings to the direct current circuit, synchronizing mechanism forperiodicallyv closing and opening the contacts in a predeterminedoverlapping succession to periodically interconnect each phase windingin parallel with the succeeding phase winding during the predeterminedclosure overlap of the corresponding contacts, capacitance means havingconnections controlled by the contacts for charging the capacitancemeans proportional to the valueof the load current flow through thecontacts during the separate closure of the contacts and for applyingthe resulting capacitance voltage to transfer a corresponding value ofload current from each phase winding to the succeeding phase windingduring the predetermined closure overlap of the corresponding contacts,and means including control windings for controlling the unsaturation ofthe successively saturable reactor means to maintain the current in eachphase winding at small instantaneous values for a suflicient timeinterval after the capacitance means effects the transfer of the loadcurrent therefrom to the succeeding phase winding to include the end ofthe predetermined closure overlap of the corresponding contacts and foroppositely presaturating the reactor means after the end of the closureoverlap of the corresponding contacts.

7. An alternating current rectifier having in combination, polyphasewindings having successive phase voltages induced therein, a directcurrent load circuit, switching means including a series of contacts,each contact having connections effective upon the closure of thecontact for interconnecting a corresponding phase winding with the loadcircuit to conduct load current thereto through the contact, saturablereactor means having connections with the contacts for successivesaturation by the load current supplied from the successive phasewindings to the direct current circuit, contact operating mechanismsynchronized with the voltages of the polyphase windings forperiodically closing and opening the contacts in a predeterminedoverlapping succession to overlap the interconnection of successivephase windings with the load circuit and thereby interconnect each phasewinding in shunt with the succeeding phase winding during apredetermined closure overlap of the corresponding contacts, capacitancemeans having connections controlled by the contacts to successivelyaccumulate charges of opposite polarity proportional to the value of theload current flowing in the direct current circuit during predeterminedcontact conductive periods and to apply the resulting voltages tocircuit connections etfective upon the closure of the contranster acorresponding value 01' load currenttrom the tact for interconnecting acorresponding phase winding to include the end of the predeterminedclosure overla COIICSPOlldID" contacts, a capacitor having an inductiveof the correspondlng contacts and for oppositely predevice forrnterconnectlng the capacitor With the success1ve saturating the reactormeans after the end of the closure phase windings controlled by thecontacts to periodically overlap of the corresponding contacts. andoppositely charge the capacitor proportional to the 8. An alternatingcurrent rectifier having in combinavalue of the load current flow uponsuccessive closure tion, polyphase windings having successive phasevoltages of the contacts to produce voltages eifective to transfer aconnections effective upon the closure thereof for interdeterminedclosure overlap of the corresponding contacts,

interconnect each phase Wrndlng in parallel with the suc Include the 6ndof the Predetermlned Closure v l p f ceedlng phase WlIldll'lg during apredetermined closure the corresponding contacts, and for oppositelypresatuoverlap of the corresponding contacts, saturable reactor ratingthe reactor means after the end of the closure overmeans havingconnections with the contacts for successive lap of the correspondingcontacts.

phase windings to the direct circuit, capacitance means R f r s Cited inthe file of this patent UNITED STATES PATENTS to the value of the loadcurrent flow from successive phase Number Name Date windings to thedirect current circuit during the successive 1,183,333 Koppitz May 23,1916 closure of the contacts and to apply the resulting voltages 1,929,70 Willis Oct. 10, 1933 to transfer a corresponding value of load currentfrom 1,929,721 Willis Oct. 10, 1933 each phase Winding to the succeedingphase Winding upon 1,929,722 Willis Oct. 10, 1933 the parallelinterconnection thereof during the predeter- 4 1,929,723 Wlllis Oct. 10,1933 mined closure overlap of the corresponding contacts, and 1,929,724Wil is Oc 10, 1933 means including control windings for controlling theun- 1,92 ,72 WllliS Oct. 10, 1933 saturation of the successivelysaturable reactor means to 1,929,726 Willis Oct. 10, 1933 maintain thecurrent in each phase winding at small in- 1,929,727 Willis Oct. 10,1933 stantaneous values for a sulficient time interval after the1,952,062 Fecker Mar. 27, 1934 capacitance means effects the transfer ofthe load current 2,036,844 Willis Apr. 7, 1936 therefrom to thesucceeding phase Winding to include the 2,141,921 Lenkert Dec. 27, 1938end of the predetermined closure overlap of the corre- 2,182,628Janetschke Dec. 5, 1939 sponding contacts and for oppositelypresaturating the 2,209,806 Bedford July 30, 1940 reactor means afterthe end of the closure overlap of 2,220,747 Westend0rp Nov. 5, 1940 thecorresponding contacts. 2,241,050 Bedford et al. May 6, 1941 nalternatim. current rectifier having in combina- 2,284,794 Bedford June2, 1942 tion, polyphase windings having successive phase voltages2,310,792 Koppelmann Feb. 9, 1943 induced therein, a direct current loadcircuit, switching 2,351,975 Koppelmann June 20, 1944 means including aseries of contacts, each contact having 5 2,476,068 Short July 12, 1949

